Electrical precipitator



July 21, 1959 H. A. WINTERMUTE 2,895,563

ELECTRICAL PRECIPITATOR Filed Feb. 28, 1955 s Sheets-Sheet 1 I INVENTOR |6c 1,. HARRY A. WINTERNUTE ATTORNEY July 21, 1959 H. A. WINTERMUTE 2,895,563

ELECTRICAL PRECIPITATOR File d Feb. 28, 1955 3 Sheets-Sheet 2 INVENTOR HARRYAWINTERMUTE BY A awz/ TM ATTORNEY July 21; 1959 H. A'. WINII'ERMUTE 2,395,563

' ELECTRICAL PRECIPITATOR Filed Feb. 28, 1955 's Sheets-Sheet 3 INVENT OR HARRY A.WINTERMUTE United States Patent ELECTRICAL PRECIPITATOR Harry A. -Wintermute, Plainfield, N.J., assignor to Research Corporation, NewYrork, N.Y., a corporation of New York Application February 28, 1955, Serial No. 490,889

'16 Claims. (Cl. 183-7) This invention relates to electrical precipitator system for removing finely dispersed solid particles from a gas by the action of an electric field or discharge, and more particularly to the provision of improved ballasting means for electrostatic precipitator circuits.

In an electrical precipitation circuit, ballasting of the circuit is of major importance. Ballast means are used to steady the circuit, prevent disruptive discharges, limit the current flow at times of arc-over in the precipitator, and act as an automatic valve to regulate current and voltage when abrupt changes in gas conditions take place in the precipitator. The type of ballasting most commonly used in electrical precipitator circuits has been non-inductive resistance ballasting. Choke coils have also been used for ballasting to a limited extent, and some high tension transformers have been built which give a very considerable ballasting action, but this introduces certain limitations as to current and voltages which are, undesirable in practical installations.

The effective ballasting action of resistors varies generally as a direct function of the ohmage value of the resistor, but the power loss in such a resistor varies, of course, as the square of the current. In large scale installations, such as are commonly employed for industrial precipitation, the current flow is high and therefore a very considerable power loss is suffered in the resistor, unless the resistance value is reduced to so low a point that the ballasting action is marginal. Due to these conditions, it is desirable to find a method of ballasting which will give a high degree of ballasting action and, at the same time, have a relatively small power loss. It is a primary object of the invention to accomplish this result by the use of transformer action. Another object is to provide an effective wide-range ballasting action by simple and rugged means, fool-proof in operation, and requiring no expensive maintenance since no complex electronic or moving electrical parts are required. Still another object is to provide an electrically efficient ballast arrangement having a very effective ballasting action, but negligible or very small power losses.

According to the invention, the primary of a ballasting transformer is inserted in series with the low tension or primary winding of the high tension transformer employed for precipitation, while the secondary of the transformer is connected essentially in parallel with the primary winding of the high tension transformer, that is, between the junction of the two primaries and the opposite side of the power line.

The specific nature of the invention, as well as other objects and advantages thereof, will clearly appear from a description of a preferred embodiment as shown in the accompanying drawings, in which:

Fig. l is a schematic circuit diagram showing the principle of the invention;

Fig. 2 is a schematic diagram of a circuit similar to Fig. 1, with more details of control features;

Fig. 3 is another modification of the same circuit; Fig. 4 shows the invention employed with a kenetron or other valve type rectification with half-wave rectification using both halves of the wave;

Fig. 5 shows the energization of a single precipitator section using half-wave rectification;

Fig. 6 shows an arrangement using a floating coil ballast transformer;

Fig. 7 shows a three-phase arrangement of precipitators using ballast transformers;

Fig. 8 shows a transformer ballast arrangement according to the invention with an additional auxiliary voltage boosting coil;

Fig. 9 shows the combined use of transformer and resistor ballasting in parallel;

Fig. 10 shows an arrangement generally similar to that of Fig. 2, but capable of finer control; and

Fig. 11 shows the use of a powerstat type of voltage regulator for controlling the voltage coil of the ballasting transformer.

It will be apparent from the following description that the principle of the invention can be applied in many forms to precipitator systems. However, the basic principle of the invention is perhaps best illustrated in Fig. 1, in which power is supplied from a commercial power line 2, 4, through ballast transformer 6 to the primary winding of a high tension transformer 8. The high voltage secondary winding of transformer 8 supplies voltage which is rectified by any suitable means, as shown at 10 and 12, to the respective discharge electrodes 14 and 16 of two precipitator sections. A grounded center tap connection 18 from the transformer to the collector electrodes of the precipitator section completes the circuit in well-known fashion. The primary or current coil 20 of the ballasting transformer 6 is inserted in series with a line and with the primary winding of transformer 8. The secondary or voltage Winding'22 of transformer 6 is connected at point 26 between winding 20 and the primary winding of transformer 8, and the other terminal of the coil is connected at 24 to the opposite side of the power line. Coil 22 usually has a great many turns as compared to the series coil 20. It is of particular importance that the terminal 26 of coil 22 is connected on the transformer side of coil 20 rather than on the power line side. Voltage boosting or bucking transformers are known in which a secondary coil is connected on the power line side of the primary coil, but such voltage boosters would not give any ballasting action to the precipitator circuit.

In the arrangement of Fig. l, the ballasting action depends upon the impedance of coil 20, which controls the boosting action of coil 22. In general, the action is as follows: With an increase in current flow due to corona flow from electrodes 14 and 16 of the precipitator, and more particularly due to arc-over, the voltage drop across coil 20 increases. Since the total voltage drop across coils 20 and primary 9 remains constant, an increase in voltage drop across coil 20 necessarily means a decrease in voltage drop in primary 9, and therefore a decrease across coil 22 which is in parallel with primary 9. The resulting voltage drop in coil 22 reduces the boosting action of this coil on the primary winding 20, which further reduces the voltage impressed on the low tension winding of the power transformer. Conversely, when the current flow through coil 20 decreases, the voltage on coil 22 increases which in turn increases the boosting action of this coil on coil 20. Thus, this type of ballasting gives a double effect instead of the single effect obtainable with resistance ballasting or impedance ballasting. By proper choice of transformer ratio, several times the ballasting action can be obtained compared to that which is otherwise possible. Practical tests of the above principle have established that the percentage of removal of solid materials from the gas beingtreated J is at least as high as when any other method of ballasting is employed, while, at the same time, the ballasting wattage losses are very much smaller than when resistance ballasting is used.

An adjustable tap switch is shown at 27 for initial adjustment of the precipitator voltage in accordance with the conditions of operation.

In the following figures, the same reference characters will be used as in Fig. 2 for corresponding parts, with a small letter subscript, i.e., transformer 8a in Fig. 2, 8b in Fig. 3, etc.

Fig. 2 shows a modification of Fig. 1, in which a variable resistance 28 is included between the coils of the transformers 6a and 8a. This resistor is preferably made variable to enable finer control of the boosting action. For independent control of the voltage requirements of coil 22a, this coil may also be connected to the various taps of the transformer primary 9a, by means of a suitable switch 30.

Fig. 3 shows the use of an auto transformer as a ballasting means. Auto-transformers are commonly provided with an internal connection as shown at 40, from which a single lead 41 is brought out to the primary of the high tension transformer 8b. Tap switches are provided at 43 and 44 for the primary winding and the voltage coil winding respectively while a similar tap switch is provided at 46 for current winding 20]) of the ballast transformer. Since the common junction 40 is inside the transformer, the ballasting resistance 42 is placed at the outer end of the current coil, so that the ballasting action of the shunt coil 22b will be affected by the IR drop of this resistance.

Fig. 4 shows a similar ballast circuit to Fig. 2 with the high tension secondary circuit employing a kenetron or other valve-type rectification, and using an induction regulator having a primary winding 20c and a secondary winding 22c movable relative to the primary so as to secure finer gradations of control than can be obtained otherwise. In this form of the invention, the employment of taps on the power transformer 80 is rendered unnecessary.

Fig. 5 is an arrangement similar to the preceding figures, showing the use of a kenetron or other valvetype rectification in a half-wave rectification arrangement and employing a shunted rectifier 50 in the primary circuit. The preceding examples are included to show the flexibility of the transformer ballasting arrangement and all include the use of a ballasting resistance placed be tween the series coil and the point where the shunt coil is attached. Note that if this resistance is placed between the current coil and the power supply, the results will be the same as with the arrangements shown. However, if the resistance is placed between the attachment point of the shunt coil and the transformer terminal, the IR drop of the resistance is then lost to the transformer ballasting.

Fig. 6 shows an arrangement using transformer ballasting with automatic voltage control. The transformer 52 used for this purpose is of the variable-voltage, constantcurrent type. The magnetic flux generated by coil 22c and the influence which this flux has on the voltage generated in coil 20c depends upon the distance between the two coils. When the two coils are in physical contact, all of the flux generated by the coil 22c passes through coil 202. However, when coil 22a is in the top position, a large percentage of the flux does not pass through coil 20e, but jumps from the center core to the outside legs and the voltage generated in coil 20c is therefore very small. A three-phase reversible speed motor 58 is employed, through suitable gearing of conventional type, to raise and lower coil 22c, under control of voltmeter type relay 60, the input leads of which, 62, are connected to suitable taps on coil 92 of the high voltage transformer 82 of the precipitator. The normal operating voltage of the precipitator is therefore controlled by transformer 52. In addition to this control, the type of transformer ballasting action previously described is obtained by connecting terminal 66 of coil 22a to a point (e.g., tap 2) after the coil 202. For example, the terminals 66 and 68 are so connected that the flux from coil 22:: causes coil 202 to increase instead of reducing the voltage to the power transformer. Alternatively, any other desired arrangement of sliding contacts 66, 67, 68 on the taps (16) may be used. The polarity reversing switch 70 is needed only when mechanical rectification is employed, driven by a synchronous induction motor, but is not needed when selenium or electronic tube rectifiers are used, or when a polarized synchronous motor equipped with permanent magnets is employed.

Fig. 7 shows a typical example of the use of the ballast arrangement of the invention with a 3-phase power source. The ballast transformers 20f, 20f", etc. are preferably induction regulators, as shown, but could in some cases also be simple booster transformers. It will be apparent that the secondary circuits of phases A, B and C, respectively, could be each connected to a separate precipitator section, in which case each such section would be provided with half-wave rectified potential, or the three phases can be connected together as shown to give full wave rectified potential. It will be apparent that two and six phase circuits can also be used as well as threephase circuits.

Fig. 8 shows a manner of obtaining improved control of the ballast voltage by the provision of a boosting voltage coil 76.

Fig. 9 shows how the ballasting transformer arrangement of the invention may be shunted by ballast resistor 78, which provides a compromise arrangement between highest efficiency and lowest cost.

Fig. 10 shows further refinements of control which may be provided for the ballast transformer. In this arrangement, adjustable resistor 83 provides separate control of coil 221, while a tap switch 81 provides separate control of the primary winding 91' independently of tap switch 26: of coil 22f. In this way, each factor affecting the voltage control can be separately adjusted to any desired point.

Fig. 11 shows a manner in which a conventional Powerstat voltage regulator 82 may be employed to control the voltage of the voltage coil of the ballast transformer.

It will be apparent that the embodiments shown are only exemplary and that various modifications can be made in construction and arrangement within the scope of my invention as defined in the appended claims.

I claim:

1. In combination with an electrical precipitator or the like having spaced precipitating electrodes, a high tension transformer and rectifier means between the secondary of said transformer and said electrodes; ballasting means in series with the transformer primary, said ballasting means comprising second transformer means having a current winding in series with the primary winding of the high tension transformer, and a voltage winding between said current winding and said primary winding in voltage boosting relationship with said current winding such that a change in current flow in the high tension transformer primary winding causes an inverse change in the voltage drop across the voltage winding, to tend to oppose said current change.

2. The invention according to claim 1, said voltage coil being connected in shunt relationship with the high tension transformer primary winding.

3. The invention according to claim 1, said ballasting means comprising adjustable transformer means including means for varying the physical relationship between said current and voltage windings to vary the flux linkages between said windings.

4. The invention according to claim 1, said high tension transformer being a polyphase transformer, said current and voltage windings being also of polyphase construction with a separate winding for each phase.

5. The invention according to claim 1, including a second voltage winding in said second transformer means connected in opposition to said first voltage winding.

6. The invention according to claim 1, and a ballast resistor in shunt relation with said current winding.

7. The invention according to claim 6, said ballast resistor being adjustable.

8. In combination with an electrical precipitator or the like having spaced electrode means, a high tension transformer and rectifier means between the secondary of said transformer and said electrodes; ballasting means in series with the transformer primary, said ballasting means comprising second transformer means having a current winding in series with the primary Winding of the high tension transformer, a voltage winding in voltage boosting relation with said current winding, and a first junction point between one terminal of said current winding and one terminal of said high tension transformer primary winding, connection means between said junction point and one terminal of said voltage winding and second connection means between the other terminal of said voltage winding and a second point on said high tension transformer primary winding whereby a change in current flow in the high tension transformer winding causes an inverse change in the voltage drop across the voltage winding thereby tending to oppose said current change.

9. The invention according to claim 8, including a series of voltage taps on said high tension transformer primary, and means for selectively connecting said second connection means to any of said taps.

10. The invention according to claim 9, including a series of taps on said voltage winding and means for connecting said second connecting means selectively to any one of said taps.

11. The invention according to claim 10, including power input lines of said precipitator, a series of taps on said current winding, and selector switch means selectively connectable to said taps for selectively connecting a desired portion of said current winding in the power circuit.

12. The invention according to claim 11, and resistance means in series with said current winding.

13. The invention according to claim 12, said resistance means being connected between said first junction point and said one terminal of the current winding.

14. In an electrical precipitator, electrode means for charging particles of a transient gas delivered therebetween, constant current means for coupling an energy potential to said electrode means including an input path, means in said input path for coupling an energy potential directly from said path to said electrodes, coil means in said path having a given IR drop with a given current flow therein, an ancillary means associated with said coil having a predetermined IR drop thereover responsive to said current flow in said path which changes inversely with the change in IR drop in said coil means to thereby maintain a substantially constant current flow in said electrode means.

15. In combination with an electrical precipitator or the like having spaced precipitating electrodes, a supply circuit including an energy potential source means, a load circuit including said spaced electrodes, inductive means for coupling said supply circuit to said load circuit including a high tension transformer, and a ballasting means in said supply circuit including a current coil in series with the primary winding of said transformer and a voltage coil in voltage boosting relationship with said current coil connected in said supply circuit behind said current coil and in parallel with at least a portion of the primary winding of said transformer whereby an increase in current flow in the primary winding of said transformer causes a decrease in voltage drop across the voltage coil which tends to oppose the current increase.

16. In an electrical precipitator, electrode means for charging particles of a transient gas delivered therebetween, constant current means for coupling an energy potential to said electrode means including an input path, at least a pair of primary windings connected in series with said input path, a booster winding connected in parallel with one of said primary windings and inductively coupled to the said other primary winding and means for delivering steady current from said one pri mary winding for said electrodes.

References Cited in the file of this patent UNITED STATES PATENTS 2,297,740 Brown Oct. 6, 1942 2,297,841 MacKenzie Oct. 6, 1942 2,767,370 Medal Oct. 16, 1956 FOREIGN PATENTS 521,316 Great Britain May 17, 1940 557,336 Great Britain Nov. 16, 1943 

